The present invention relates to a recording medium in the form of a tape cassette containing a magnetic tape, a tape drive apparatus capable of recording and/or reproducing information to and/or from the tape cassette, and a recording and/or reproducing method for use with the tape drive apparatus.
Tape streamer drives are a well-known drive apparatus for recording and reproducing digital data to and from a magnetic tape serving as a recording medium held in a tape cassette. Depending on the tape length of the tape cassette they use, some tape streamer drives can record large quantities of data amounting to tens to hundreds of gigabytes. Their mass storage capability allows the tape streamer drives to be utilized extensively in diverse applications including the backup of data recorded illustratively on hard discs in the computer body and the storage of picture data and other massive data.
In a data storage system made up of such a tape streamer drive and a tape cassette containing a magnetic tape, management information or the like is needed for the drive to manage appropriately its recording and/or reproduction of data to and/or from the magnetic tape. The management information includes information about diverse locations on the magnetic tape as well as a use history of the tape.
A management information area is located at the beginning of the magnetic tape or at the beginning of each of the partitions formed along the tape. Before writing or reproducing data to or from the magnetic tape, the tape streamer drive gains access to the management information area to read necessary management information therefrom. Based on the management information thus retrieved, the tape streamer drive performs various processes allowing subsequent recording or reproducing operations to proceed appropriately.
At the end of the data recording or reproduction of data, the tape streamer drive again accesses the management information area to update the relevant information therein in a manner reflecting any changes resulting from the preceding recording or reproducing operation. The updates are carried out to prepare for the next recording or reproducing operation. Thereafter, the tape cassette is unloaded and ejected from the tape streamer drive.
Where recording and/or reproduction is performed on the basis of such management information, the tape streamer drive is required twice to access the management information area at the beginning of the magnetic tape or of one of its partitions: first, before the operation is started, and later, when the operation has ended, so that the relevant data should be written to and read from the area each time. In other words, the tape cassette cannot be loaded or unloaded halfway through the recording or reproducing operation along the magnetic tape.
Upon access to the management information area, the tape streamer drive is required physically to feed the magnetic tape. That means it takes some time to access the beginning of the magnetic tape or one of its partitions. In particular, if the recording or reproducing operation on the magnetic tape ends at a considerable physical distance from the management information area, it takes a correspondingly long time to feed the tape before the target area can be reached.
As described, data storage systems that utilize tape cassettes as their recording media require a relatively long access time before a single write or read operation is completed, i.e., from the time the magnetic tape was loaded until it is unloaded. It is obviously preferable to minimize the time required for such a series of access-related operations.
For that purpose, techniques have been proposed whereby a nonvolatile memory is installed within a tape cassette enclosure so that the memory may accommodate management information (refer illustratively to Japanese Patent Laid-Open No. Hei 9-237474).
The tape streamer drive for use with such a memory-equipped tape cassette incorporates an interface for writing and reading management information to and from the nonvolatile memory, i.e., information about the recording and reproduction of data to and from the magnetic tape.
The above arrangement eliminates the need illustratively to rewind the magnetic tape at the time of loading or unloading of the cassette. That is, the tape cassette may be loaded or unloaded halfway through the ongoing operation along the tape.
The above-mentioned nonvolatile memory was attached to the tape cassette initially as an auxiliary memory to gain advantages such as the shortened access time. Even if such a nonvolatile memory is not utilized, however, normal-use cassette tapes still permit writing and reading of data thereto and therefrom. If the nonvolatile memory is to be employed for more specific purposes, it is possible to conceive various types of tape cassettes for special uses.
The tape cassettes for one of such special purposes are illustratively those to which data are recorded only once. Once recorded on the tape, the data can only be read and not overwritten. This tape cassette feature is called WORM (Write Once Read Many). The WORM feature is also provided to disc type recording media, such as CD-Rs and DVD-Rs.
On a WORM tape cassette, data can only be read from the data-recorded areas and no data can be written thereto. History information about the read and other operations on the tape cannot be updated in a manner causing any management information area associated with the recorded areas to reflect the past changes. Such history information can only be written to the nonvolatile memory in the tape cassette. That is, where a WORM tape cassette is subject to the recording and/or reproduction of data, it is mandatory to use the management information held in the nonvolatile memory of the cassette, and not any management information recorded on the magnetic tape.
If the presence of a nonvolatile memory in a cassette is assumed as a prerequisite, it is possible to come up with tape cassettes for various special purposes that necessitate the mandatory use of that memory. In particular, special-use tape cassettes are suited for applications that require restricting the recording or reproduction of data to or from the magnetic tape. The data to be recorded on the magnetic tape housed in such special-use tape cassettes often demand much higher security than the data to be accommodated by normal-use tape cassettes.
Illustratively, WORM tape cassettes are actually utilized most often for the recording of important data that call for secure measures to maintain their high storage value, given the premise that recorded data can only be read and neither overwritten nor erased. Hence, the high levels of security that are demanded by and offered to the data accommodated by the WORM tape cassettes.
As described, special-use tape cassettes typified by the WORM tape cassette above serve their purposes when each is furnished with a nonvolatile memory. The memory is physically placed illustratively inside the tape cassette enclosure.
That structure raises the possibility of fraud: the nonvolatile memory within a special-use tape cassette could be replaced with an illegally procured memory, whereby the WORM feature could be disabled. This tampering could lead to falsification of data recorded on the magnetic tape.
Such an eventuality requires additional suitable measures to prevent the fraud illustratively involving illegal replacement of the nonvolatile memory, before the special-use tape cassettes can be actually marketed.